![]() When that is done properly, I would expect the reported torque to be within 2-3% of actual.Īn added bonus will be a stiffer, more stable speed under changing load conditions if you tune up the speed loop controller properly. To get the drive to report torque, you will need to reprogram the drive to run in sensorless vector mode. Better to let the drive do the math and report the torque for you. It is not a simple proportion but rather a vector sum which involves some calculation. The tricky part is determining the motor torque when the load and the current are less than full load. Lets calculate the mechanical horsepower of a machine with a 150 N.m torque value and 1500 rpm speed: Power (W) 150 N.m 1500 rpm 23,563 Watts. That's assuming the drive is set for constant V/Hz. When we want to convert gross torque to horsepower, we need know the formula of power in Watts: Power (W) Torque (N.m) Speed (rpm) / 9.5488. That will be true for any frequency from 10 to 60hz. You can pretty well figure that the motor is producing its rated nameplate torque of about 30ft-lbs when it is drawing 13.5amps. Use the VFD display instead.Īlso, as skogsgurra has said, you need to know exactly what the drive display is telling you, especially if the display values are in percent (percent of what?). RE: Calculating Motor Torque on VFD Skogsgurra (Electrical) 23 Jan 08 09:52Īs skogsgurra has already said, do not try to measure anything on the motor leads. MOTOR TORQUE Calculator-1 Known variables: Horse Power and Speed in RPM Torque is the action of a force producing or tending to produce rotation. Will the unbalanced line affect this besides heating up the buss diodes? Which reading can I believe to calculate torque at 25 hertz?ĭo I need to get another amp meter to read the 5khz carrier? Voltage from phase to phase, 480 V, 480 V, 460 V The load is pulsing at about 1 hz which is reflected in the amp draw. (Refer to the below sections on calculations for each.) Once you've calculated the inertia, torque and speed for the motor you'll select the type of motor based on the required specifications. He is getting someone to fix the unbalanced incoming line. In order to determine the performance you'll need from the motor, there are three factors to calculate Moment of Inertia, Torque and Speed. The customer is going to change the ratio to run the motor at 60 hz after testing and wants to calculate how much torque he is really using. ![]() ![]() The following reading were taken by a old clamp on amp/volt meter, Simpson I think, which does not have very fine scale for reading voltage. When we want to convert gross torque to horsepower, we have to know how many watts are in one horsepower for that particular type of device (e.g., in an electric motor, 1 horsepower equals 746 Watts). ![]() The motor is being driven by a WEG VFD in the volts/hertz mode, (not vector) at 25 Hz. Our horsepower calculator can help you calculate power in horsepowers. A customer has a 10 hp, 480 V, 3 ph, Baldor Motor # CWDM3714T driving a mixer through a 100:1 helical gearbox. ![]()
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